Many closed fluid containment and transport systems require protection against damage caused when freezing temperatures cause their fluid contents to freeze, thereby cracking or rupturing their containment systems, particularly where coils, pipes, and other equipment are exposed to temperatures that drop below freezing.
One example is outdoor or underground water pipes in Northern climes during the winter. This need is even greater where below-freezing temperatures are sustained for long periods of time. Another example relates to the practice of “winterization” of commercial building air-handler coils inactivated during the winter months. Coil winterization involves replacement of residual water from coil low spots with an antifreeze solution to prevent bursting upon coil exposure to incoming, unheated building supply air. Similarly, other liquid containment and transport systems and liquid storage systems can benefit from features that prevent their contents from freezing, and thus avoid temperature-related damage to or compromise of their containment systems. Even where the integrity of the containment system is not of concern, frozen solids such as ice crystals may impair the flow of the unfrozen portion of the liquid. When freezing is sufficient to block liquid flow, the frozen solids usually must be unfrozen before resuming fluid flow through transport systems. There are also other situations where it is desirable to keep a liquid, such as water, in a liquid state at a temperature below its normal freezing point.
It can be especially desirable to provide protection to equipment and vessels that transport or store chilled liquids. As chilled liquids generally reach their freezing points and transition from liquid to solid form faster than the same liquids maintained at ambient temperatures, additional anti-freezing protections to these systems may prevent these liquids from freezing when exposed to relatively modest decreases in temperature.
There are a number of insulating systems that provide some protection against the effects of extremely cold temperatures in fluid containment and transport systems. Anti-freeze solutions for these types of systems are typically made from ethylene or propylene glycols. However, glycols can degrade into glycolic acid, which is known to lower pH and to accelerate corrosion. Ethylene glycol is subject to both microbial and chemical degradation. Other systems allow the short-term use of glycol-based anti-freeze solutions, but require the glycol to be thoroughly flushed from the system before resuming normal operation. In many instances, relatively small amounts of glycol used to protect very small volume system components is not flushed, or not adequately flushed, resulting in the development of acidic and/or highly unfavorable biological conditions throughout an entire equipment system or an entire building system. Mitigating glycol decomposition related problems can lead to significant expense in flush water, man-hours and corrective chemical addition. Glycol-based anti-freeze solutions can be costly to prepare and maintain, and may not be compatible with some cooling systems. Furthermore, ethylene glycol is known to be toxic to human beings.
There is a need for alternatives to the formulations that are currently used to preserve the integrity of systems that transport, store, or contain liquid when exposed to below-freezing temperatures and a particular need for formulations that avoid the corrosive effects known in current glycol-based formulations. There is a need for an inexpensive chemical anti-freeze formulation that will minimize liquid waste, maximize energy savings, protect equipment and machinery, and minimize health and safety risks, particularly for anti-freeze formulations that can be applied to mechanical systems that transport or store liquids.
Nitrite (NO2) and nitrate (NO3) solutions have been used to cool large volumes of water in thermal energy storage systems. However, this application has been limited to cooling volumes of water, not to preserving the equipment containing or transporting the water.
Further economic savings and other advantages could be achieved with improved nitrite/nitrate formulations used to improve the integrity of liquid containment and transport systems.